Improvement in compositions for tanning



UNITED STATES PATENT OFFICE. V

SENECA PIERCE AND F. F. BEARDSLEY, OF CASTLE GROVE, IOWA.

IMPROVEMENTEIN COMPOSITIONS FOR TANNING.

Specification forming part of Letters Patent No. 25,671, dated October 4, 1859.

To all whom it may concern:

Be it known that we, SENECA PIERCE and FREDERICK F. BEARDSLEY, both of Castle Grove, in the county of Jones and State of Iowa, have invented a new and useful Composition for Tanning Hides and Skins; and we do hereby declare that the following is a full, clear, and exact description of the same.

The objects of our invention are, first, to tan skins and hides by a short and cheap process; second, to use substances that are unlimited in supply to take the place of our common barks, which are becoming scarce and dear; third, to make flexible leather close in the pores through the agency of a tanning compound of which terra-japonica constitutes a part, which has not hitherto been done; fourth, the prevention, as far as possible, of hygrometric action in theleather made by our composition.

The nature of our invention consists in the employment of a compound of terra-japonica, alum, (sulphate of alumina,) Glaubers salt, (sulphate of soda,) and saltpeter (nitrate of potassa)disso1vedin waterin certain proportions, hereinafter specified,for the purpose of tanning skins and hides and converting them into very superior leather by a short and cheap process, as hereinafter more fully described.

To enable others skilled in the art to make our tanning compound and to use the same, we will describe it as clearly and briefly as possible.

After skins are prepared for tanning by unhairing, &c., in the usual manner, we make up a liquid for them of the following substances: terra-japonica, (catechu,) one pound; alum, three ounces; Glaubers salt, two and one-fourth ounces 5 saltpeter, one-fourth ounce. These are all dissolved together in about one gallon of soft water to form 'our tanning compound. The quantity stated will tan a large calf-skin when the liquor is made' up in the vats but when the liquors are first commenced, or are what is called fresh, it will take twice this quantity for one skin. A small difference in the proportions stated will not materially alter the result; but thus far we have found these to produce the best effects.

lVe will describe the method of tanning one skin by our composition, but any number may be operated upon in the same manner, only requiring a greater amount of the substances specified.

We place, for one skin, as much soft water in a vat as will cover it and then add about one quart of the gallon of our composition described. The skin is now entered and moved rapidly in the liquid for about half an hour. Then another quart is added and the handling continued for a few hours longer, when another quart is added and the movement conducted more slowly, with intervals of repose, thewhole concentrated liquid being added in about two days, when the calf-skin will be found perfectly tanned. Calf-skins are tanned by our composition in this manner in about two days,kip-skinsin aboutfourdays,andother skins and hides in proportion to their thickness.

Our composition is made up, as described, in any quantities, and added to the liquor in the tanning-vats as the tanner sees the liquor becoming weak. The practical tanner knows by personal examination when the skin has become perfect leather and is thoroughly tanned. There is no other method of determining when the process is completed.

We have found that skins and hides have a great affinity for the ingredients in our tanning-liquor. They absorb the tannin rapidly, and combine with it in such harmonious proportions as to make very superior leather.

The substances specified appear to exert the following actions in the tanning process: The Glaubers salt opens the pores of the skin and keeps it soft and free from wrinkles. The alum has a plumping effect, while at the same time it is of a tanning character in combining chemically to produce an insoluble compound with the gelatine of the skin. The terra-japonica contains the tannin in a greater quantity than any other known substance. The saltpeter appears to exert an antiseptic infiuence. It has long been used in the preservation of meat, and we have found it useful in preserving our liquors for a long period of time. Leather tanned with terra-japonica is liable to be porous, but the saltpeter seems to exert an influence to make it close in the texture. Gallic acid is liable to be formed in tannin-liquids of simple terra-japonica, but no such result seems to follow its use in our combined liquor. Common salt has been used in various tanning-liquors,but it is liable to render the leather an absorbent of moisture. Hence Glaubers salt is a superior substitute.

Our composition will make as good leather from skins in a few days as can be done by some other process in as many weeks. The quality of our leather is also very good. It is close in the grain, flexible, and not liable to crack. Heretofore short tanning processes have not been very successful. They have generally rendered the leather brittle, and therefore of a very inferior quality. Our tanning composition seems to obviate this evil, while at the same time it is cheap and produces leather of superior qualities. 

